So sánh phương pháp

	Lấy mẫu chuỗi giới thiệu – Lấy mẫu quả cầu tuyết	Chọn mẫu có chủ đích
Lĩnh vực	Phương pháp luận khảo sát	Phương pháp luận khảo sát
Họ	Process / pipeline	Process / pipeline
Năm ra đời	1961	Formalized ~1980–1990
Người khởi xướng	Leo A. Goodman	Michael Quinn Patton (systematic articulation); roots in early qualitative inquiry
Loại	Non-probability sampling technique	Non-probability sampling strategy
Công trình gốc	Goodman, L. A. (1961). Snowball sampling. Annals of Mathematical Statistics, 32(1), 148–170.	Patton, M. Q. (1990). Qualitative Evaluation and Research Methods (2nd ed.). Sage. ISBN: 978-0803937796
Tên gọi khác	chain-referral sampling, network sampling, respondent-driven sampling, referral sampling	judgmental sampling, selective sampling, criterion-based sampling, purposeful sampling
Liên quan	3	4
Tóm tắt	Snowball sampling is a non-probability recruitment technique in which initial participants (seeds) refer the researcher to others who meet the study criteria, and those referrals in turn refer further participants. The sample grows incrementally — like a rolling snowball — until the required size or theoretical saturation is reached. It is the method of choice when a target population has no accessible sampling frame, such as undocumented migrants, illicit drug users, survivors of stigmatised experiences, or members of closed professional networks.	Purposive sampling is a non-probability strategy in which the researcher deliberately selects participants, documents, or cases that are information-rich with respect to the research question. Rather than drawing units at random, the researcher applies explicit criteria aligned with the study's purpose, maximising the depth and relevance of the data collected. It is the default sampling logic in most qualitative research designs and is also used in mixed-methods and applied evaluative work.